Automatic transmissions, especially for motor vehicles, include, in accord with the state of the technology of planetary gear sets and which are shifted by friction based shifting elements, such as clutches and brakes, which are customarily connected with a start-up element, which is augmented by a converter lock-up clutch, which may be, for example, a hydrodynamic torque converter or a fluid clutch.
Within the framework of DE 101 15 983 A1 of the applicant, for example, a multi-speed transmission is described, having an input shaft which is bound to an input-side gear set, and possesses an output shaft, which is connected with an output-side gear set, and has a maximum of seven shifting elements, by the selective shifting of which, at least seven forward gears (without range shifting) can be effectively shifted into. The input-side gear set is composed of a shiftable or a non-shiftable planetary gear set or, alternately, be composed of two non-shiftable, mutually coupled planetary gear sets. The output-side gear set is designed as a two carrier, four shaft transmission with two shiftable planetary gear sets and four free shafts. The first free shaft of this two-carrier, four shaft transmission is bound to the first shifting element, the second free shaft is connected to both the second and third shifting elements, the third free shaft engages the fourth and fifth shifting elements and finally, the fourth free shaft is bound to the output shaft. In the case of a multi-speed transmission with a total of six shifting elements, in accord with the invention, it has been proposed that the third free shaft or the first free shaft can be bound additionally with a sixth shifting element. In the case of a multi-speed transmission with a total of seven shifting elements, in accord with the invention, it can be proposed that the third free shaft be bound additionally to a sixth shifting element and the first free shaft be additionally connected to a seventh shifting element.
A plurality of other multi-speed transmissions are, for example, also disclosed by DE 101 15 995 A1 of the applicant, wherein four shiftable, mutually coupled planetary gear sets and six or seven frictional shifting elements are provided, the selective engagements of which, a speed of rotation of the input shaft of the transmission is to be transmitted to an output shaft, so that nine or eleven forward gears and at least one reverse gear stage can be attained. In accord with the accompanying transmission diagram, in each shifting stage two of three shifting elements are engaged, whereupon, a change from one gear to an immediately next higher successive gear, or to an immediately next lower gear, in order to avoid range shifting, respectively only one engaged shifting element need be disengaged and a previously disengaged element can be engaged.
Further in the generic, unpublished patent application DE 10 2005 002 337.1 of the applicant, a multi-speed transmission with one input shaft, one output shaft, four mutually coupled single planetary gear sets and five shifting elements are proposed, whereby eight forward gears can be employed, these being free from range shifting, and shifted into in such a manner, that during one gear change from a forward gear into the next successive higher or lower forward gear, only one of the previously engaged shifting elements need be disengaged and only one of the previously disengaged shifting elements need be engaged. This known multi-speed transmission possesses also a reverse gear. In all forward gears as well as in the reverse gear, three shifting elements are engaged. Relative to the kinematical coupling of the four planetary gear sets among each other as well as to the shafts for input and output, provision has been made to the effect that: a carrier of the fourth planetary gear set is connected to the input shaft to form a first shaft of the transmission, a carrier of the third planetary gear set and the output shaft are bound together to form a second shaft of the transmission, a sun gear of the first planetary gear set and a sun gear of the fourth planetary gear set are connected together to form a third shaft of the transmission, a ring gear of the first planetary gear set forms a fourth shaft of the transmission, a ring gear of the second planetary gear set and a sun gear of the third planetary gear set are bound together to form a fifth shaft of the transmission, a carrier of the first planetary gear set and a ring gear of the third planetary gear set are bound together, to form a sixth shaft of the transmission, a sun gear of the second planetary gear set and a ring gear of the firth planetary gear set are bound together to form a seventh shaft of the transmission and, finally, a carrier of the second planetary gear set forms an eighth shaft of the transmission. Relative to the kinematical coupling of the five shifting elements to the four planetary gear sets and to the input and output shafts, provision has been made to the effect that: the first shifting element can be placed in the power-flow path between the third shaft and the housing of the transmission, the second shifting element can be placed between the fourth shaft and the housing of the transmission, the third shifting element can be placed between the first and the second shafts, the fourth shifting element can be placed either between the eighth and the second shafts, or between the eighth and sixth shafts, and finally the fifth shifting element can be placed either between the seventh and fifth shafts or between the seventh and eighth shafts, or yet between the fifth and eighth shafts.
Automatically shiftable vehicle transmissions, which are based on planetary gear arrangements, are generally of the currently accepted state of the technology, and consequently the subject of frequent descriptions and are continually being developed and improved. Accordingly, these transmissions should possess a sufficient number of forward gears as well as at least one reverse gear. Advantageously, these known transmissions also should have a very satisfactory ratio with a high degree of spread, as well as favorable steps between gears. In addition, these transmission should enable a high startup and acceleration ratio in a forward gear and a have a direct gear for use in both passenger vehicles and trucks. Beyond this, these transmissions should be manufactured with a small cost and little effort and require a minimal number of shifting elements and, where sequential shifting is required, avoid double shifting, so that for shifting in defined gear-ranges respectively, only one shifting element need be changed.